1. Field of the Invention
The present invention relates to optical to electrical and electrical to optical converter modules. In particular, the invention relates to a module that is aligned after assembly.
2. Description of Related Art
Optical transmitter modules that convert electrical signals in wires into optical signals in fibers are known. Optical receiver modules that convert optical signals in fibers into electrical signals in wires are known. Optical transceiver modules that both convert electrical signals in wires into optical signals in fibers and convert optical signals in fibers into electrical signals in wires are known. Alignment architectures for these known modules may be regarded in two categories: fiber in line with the optical source/detector and fiber perpendicular with the optical source/detector. The optical source is generally some kind of laser, and the optical detector is typically a photodiode or phototransistor, or equivalent. The optical alignment of the fiber with the optical source/detector for these modules is exceedingly demanding, particularly for singlemode fibers in which the fiber core is less than 10 μm in diameter and the acceptance angle is narrow.
In known assembly processes for a transmitting module, the module assembly process is interrupted for “in-line” alignment. During the alignment procedure the module's laser is turned on, and the fiber output is connected to a power meter. The parts are moved either manually or robotically to achieve maximum coupling of the light into the fiber, then the components are permanently fixed in place. Then, the module assembly process is continued to provide the finished module. At the end of the module's assembly process, the laser is again turned on and the module's fiber is connected to a power meter. Similar assembly practices apply to optical receiver and transceiver modules.
This assembly practice is referred to as the in-line alignment process. The in-line alignment process requires that electrical and optical connections from test equipment to the module under assembly be made before assembly is complete. The in-line alignment process is relatively costly. What is needed is a way to defer alignment until assembly is complete, and the module is in final test. Then, the alignment should be fixed in position.
Furthermore, after the module has been assembled and the alignment fixed in position, the components of the module may drift out of alignment due to aging of the structure and bonding materials, or due the temporary or permanent degradation from thermal expansion, shock or vibration. What is needed is a way to realign the module components after the module assembly is complete and after the module had been initially aligned and the alignment fixed in position. Then, the alignment should be re-fixed in position.